This invention relates to a circuit arrangement for operating a discharge lamp comprising
an oscillator for generating a high frequency input voltage, PA1 a piezo-electric transformer equipped with input terminals coupled to the oscillator and output terminals, PA1 a load circuit coupled to the output terminals of the piezo-electric transformer and comprising terminals for lamp connection.
The invention also relates to a liquid crystal display comprising such a circuit arrangement.
Such a circuit arrangement is known from EP 0706306 A2. The known circuit arrangement is very suitable to be used for operating the type of low pressure mercury discharge lamp that is used as back light in a liquid crystal display. These low pressure mercury discharge lamps have a relatively high ignition voltage and also a relatively high operating voltage. An important advantage of circuit arrangements incorporating a piezo-electric transformer is that the frequency of the high frequency input voltage can be maintained at the same value during both ignition and stationary operation. This has the advantage that the configuration of the circuit arrangement can be relatively simple. Another important advantage is that since a piezo-electric transformer is generally very small, the circuit arrangement in turn can also be very small. A disadvantage of the known circuit arrangements is that for them to be able to dim the lamp, they need to comprise relatively complicated dimming circuitry. This relatively complicated dimming circuitry renders the circuit arrangement expensive and bulky.